For growing a monocrystal by a CZ(Czochralski) method, there has been known a method for injecting germanium (Ge) as a secondary dopant in addition to a primary dopant such as red phosphorus (P) and arsenic (As).
Because Ge is solid at normal temperature, Ge is typically directly dropped into a semiconductor melt in a crucible.
However, when a solid material is directly dropped into a semiconductor melt, the semiconductor melt spatters due to the drop, and foulings on a chamber or a furnace are dropped off during pulling up a crystal, which hampers monocystallization. Further, when a solid material is dropped into the semiconductor melt, gas is introduced thereinto together with the drop of Ge and pinholes are generated, thereby lowering a yield rate of monocrystals.
Thus, Patent Document 1 has suggested that a low-melting-point dopant such as Ge is loaded into a low-melting-point-dopant injection tube which has a side wall and an upper portion hermetically sealed and has a grid-like net formed on a lower portion, and the low-melting-point-dopant injection tube is soaked in a semiconductor melt, so that the low-melting-point dopant is melted by heat of the semiconductor melt and mixed with the semiconductor melt (for example, see Patent Document 1).
Patent Document 1: JP-A-2004-137140